Add --label argument to soongdbg to call jq for metadata

With this you can choose any of the debug data that soong prints to
display in your graph.

Test: soongdbg between android.content.pm.flags-aconfig PackageInstaller --label '"sdk_version="+.properties.Sdk_version'
Change-Id: I96a25beeb0f5ea0dfd024c51aef1c4f0b2ec046c